During the last year over 450 peptides have syntesized for 50 investigators in the NIAID. Many of the peptides have been made for collaborative projects. In collaboration with David Margulies, tritium labeled peptides for binding studies with MHC class I molecules have been synthesized. Antipeptide sera have been made for the continued study of the human and mouse T cell receptor and CD3 molecules in collaboration with John Coligan and his collaborators. In collaboration with Louis Miller, the immune response to the malaria parasite has been analyzed. Peptides have been used to help determine that the major epitope recognized by T helper cells in the circumsporozoite protein is variable between different variants of Plasmodium falciparum. In addition to the T helper recognized epitope, peptides have been used to define an epitope recognized by cytotoxic T cells in the circumsporozoite protein. In collaboration with Ron Schwartz the definition of a second epitope recognized by T helper cells in the cytochrome C molecule has been completed. Fifty-three variants of this epitope were synthesized in order to define the amino acid residues that interact with the T cell receptor and those that interact with the MHC class II molecule. In collaboration with Mario Gorziglia peptides and antipeptide sera were used to define epitopes in the VP7 and VP3 proteins of human rotavirus that are recognized by neutralizing antibodies.